Studying the Brain

• EEG stands for electroencephalogram which is a recording of general brain activity usually linked to states such as sleep and arousal.

  • During an EEG test, small sensors are attached to the scalp to pick up the electrical signals in the brain which represent neuronal activity. 
  • The primary function of this is to indicate whether brain wave activity is rhythmic or not.
  • Differing numbers of electrodes can be used depending on focus of the research.
• EEG Evaluation  

  • safe way of measuring brain activity
  • helps to identify activity in various regions of brain
  • used to diagnose patients with epilepsy
  • cheaper than fMRI
  • lacks precision in measuring individual action potential of neurons as the electrodes are not sensitive enough as they are on the scalp 
  • has low spatial resolution - you cannot pinpoint the exact location of the activity
• Within the EEG data psychologists can isolate brain waves that have responded to specific stimuli. These responses are called Event Related Potentials (ERPs).

  • Electrodes are places on the scalp that detect neuronal activity whilst a stimulus is presented by the researcher.
  • An ERP is an electrical response to a specific sensory, cognitive or motor event.
  • ERPs are elicited by specific stimuli presented to the participant.
• ERP Evaluation

  • Possible to specifically detect an area responding to a specific stimuli – can support claims of localisation of function.
  • They have high temporal resolution compared to fMRI: hardly any time delay between activity and reading. 
  • Cheaper than fMRI.
  • Background noise or visual stimulation must be completely eliminated in order to establish valid data, this can take a lot of time and effort. 
  • Has low spatial resolution. 
• Functional magnetic resonance imaging (fMRI) is a functional neuroimaging procedure that measures brain activity by detecting changes with oxygenated blood flow. This technique relies on the fact that when an area of the brain is in use, blood flow to that region increases. It uses a magnetic field and radio waves to monitor the change in the energy released by haemoglobin in the blood. This method creates a detailed, moving, 3D image. Activity in regions of interest can be compared during a base line task and during a specific activity.
• FMRI Evaluation

  • a relatively objective way of measuring brain activity that is risk free as there is no radiation involved.
  • only method that allows us to view images of the brain whilst active.
  • poor temporal resolution as there is a 5 second time lag between the activity and the image actually showing on the screen. 
  • cannot detect activity of particular neurotransmitters.
  • there is a possibility that the blood flow represents communication between areas.
  • fMRI research is expensive leading to reduced sample sizes which negatively impact the validity of the research.
• A post-mortem examination / autopsy

  • The examination of a body after death
  • The aim is to determine the cause of death, but they are used in research to correlate structural abnormalities to behaviour. 
  • Carried out by pathologists (doctors who specialise in understanding the nature and causes of disease)
  • Brains that are subjected to a post mortem are likely to be of individuals who had a rare disorder or have experienced deficit in mental processes.
  • They are then compared to a ‘neurotypical’ brain in the non clinical population so conclusions about localisation of function can be made. 
• Post Mortem Evaluation –

  • Vital in establishing areas of the brain that are specialised for particular cortical function.
  • Gives the advantage of investigating brain activity in humans rather than generalising from animals. 
  • Post-mortem examinations may lack validity due to small sample sizes (as special permission needs to be granted).
  • It can be difficult to establish cause and effect from post mortem examinations. Observed damage to the brain may not be linked to the deficit that was being studied. 
  • Raises ethical issues of informed consent - cannot give consent.